1. Field of the Invention:
The present invention relates to slide fasteners, and more particularly to a fluid-tight (airtight or watertight) slide fastener stringer.
2. Prior Art:
Airtight and watertight slide fastener stringers have been known which generally comprise a support tape made of a fluid-tight soft material, and a row of discrete coupling elements mounted on the tape along an inner longitudinal edge portion thereof; such tape margin is folded so as to provide therealong a contact portion engageable with a corresponding contact portion of a like companion stringer to effect a fluid-tightness between the two stringers. When the opposed coupling element rows of the two stringers are interengaged by a slider to close the fluid-tight slide fastener, the opposed contact portions are pressed tightly against one another. The common problem with this type of fluid-tight stringers is that, during their interengagement, the individual coupling elements are subjected to objectionable deformation or displacement due to undue stress induced by the tight pressing between the opposed contact portions and even by external forces exerted on the tapes. This objectionable deformation or displacement of the coupling elements not only causes nonsmooth movement of the slider but also impairs fluid-tightness between the opposed stringers. U.K. Pat. No. 723,998, issued Feb. 16, 1955 to F. Mulka, is believed to exemplify the prior art.